Isolation and characterization of biliary epithelial cells from rainbow trout liver

Summary Lectin binding and density gradient centrifugation were explored for isolating epithelial cells from trout liver. Hepatocytes exhibited preferential attachment to coverslips coated withPhaseolus vulgaris erythroagglutinin. Biliary epithelial cells attached with glycine max agglutinin; however, significant attachment of cellular debris limited the use of glycine max agglutinin. Percoll-density gradient centrifugation separated liver cells into two distinct populations with biliary cells and hepatocytes banding at densities of 1.04 and 1.09, respectively. A discontinuous gradient composed of 13% Ficoll (wt/wt) separated biliary cells from hepatocytes. The recovery of highly enriched biliary epithelial cells from trout liver using Ficoll gradients yielded approximately 8 million cells (0.1 ml packed cells) from 10 g liver. Western blot analysis demonstrated that the cytokeratin profile for extracts from biliary epithelial cell-enriched populations differ significantly from those seen with whole liver extracts or with extracts from hepatocyte-enriched populations. Ficoll-gradient purified biliary cells and hepatocytes attached to culture plates coated with trout skin extract and carried out linear incorporation of leucine into protein and thymidine into DNA for 24 h. A mixture of growth hormones (insulin, epidermal growth factor, and dexamethasone) stimulated thymidine incorporation into DNA; however, long-term culture of dividing biliary epithelial cells was not achieved. Chemical analysis of neutral and acidic glycolipids indicated that hepatocytes and biliary cells have similar glycolipid profiles with an exception in the region of GM3 mobility, which is attributable to differences in the ceramide moiety. These studies provide a starting point for further characterization of unique cell types of the trout liver that may be important in their response to toxic and carcinogenic agents.     

Short-chain organic acids at ph 5.0 kill Escherichia coli and Salmonella spp. without causing membrane perturbation

When strains of Escherichia coli K12 and Salmonella spp. were incubated with 0.5-0.7 mol/l formic or propionic acid at pH 5.0, propionic acid was more active than formic acid. It killed 90% of the cell population within 60 min compared with over 3 h for formic acid. Cell death was not associated with a reduction in culture turbidity or a loss of membrane integrity since morphologically normal membranes were observed by electron microscopy and only a small proportion of the cytoplasmic enzyme beta-galactosidase leaked into the supernatant fluid of acid-treated E. coli K12 cultures.     

Plastron respiration in bugs and beetles

In the naucorid bug, Alphelocheirus, the plastron hairs are twice as thick and nearly twice as dense (ca. 4 × 10⁶/mm²) as they had been thought to be by previous workers. From experiments and calculations it seems clear that when the plastron is subjected to excess pressures it is wetted long before there is any question of the collapse of the hair pile itself. The plastron of Aphelocheirus is thus like the plastrons of other insects in that it is wetted long before the structures supporting the air film collapse.A plastron has been independently evolved in at least five subfamilies of the Naucoridae. A plastron is here recorded for the first time in bugs of the family Helotrephidae.It has been claimed that the plastron-bearing elmid beetles are unable to fly. Many, if not most, of these beetles fly after they emerge from their pupal cells. However, once they have begun to live under water they cease to be able to fly: the flight muscles degenerate, and this degeneration seems to be irreversible.The structure of the plastron scales of several kinds of weevils is described. The resistance of the plastron of the rice water weevil, Lissorhoptrus, to wetting at excess pressures is examined. An explanation is advanced to account for the fact that weevils and other plastron-bearing beetles that live in still waters can often swim whereas those, like elmids and dryopids, that live in running waters cannot swim.